Common names of Milk Thistle include, Mary Thistle or Holy Thistle. Milk Thistle is sometimes called silymarin, which is actually a mixture of the herb's active components, including silybinin (also called silibinin or silybin). Silymarin, which can be extracted from the seeds (fruit) of the milk thistle plant, is believed to be the biologically active part of the herb. The seeds are used to prepare capsules, extracts, powders, and tinctures. Milk thistle is a flowering herb that is native to the Mediterranean region but now flourishes in many parts of the world. It has been used for thousands of years as a remedy for a variety of ailments.